Nato plans to open a new supply route to Afghanistan through Russia and Central Asia in the next eight weeks following a spate of attacks on its main lifeline through Pakistan this year, Nato and Russian sources have told The Times.

Kazakhstan and Uzbekistan, the former Soviet Central Asian states that lie between Russia and Afghanistan, have agreed in principle to the railway route and are working out the small print with Nato, the sources said.

“It'll be weeks rather than months,” said one Nato official. “Two months max.”

The “Northern Corridor” is expected to be discussed at an informal meeting next week between Dmitri Rogozin, Russia's ambassador to Nato, and Jaap de Hoop Scheffer, Nato's Secretary-General.

The breakthrough reflects Nato and US commanders' growing concern about the attacks on their main supply line, which runs from the Pakistani port of Karachi via the Khyber Pass to Kabul and brings in 70 per cent of their supplies. The rest is either driven from Karachi via the border town of Chaman to southern Afghanistan - the Taleban's heartland - or flown in at enormous expense in transport planes that are in short supply.

“We're all increasingly concerned,” Admiral Mike Mullen, Chairman of the US Joint Chiefs of Staff, told reporters on Wednesday. “But in that concern, we've worked pretty hard to develop options.”

The opening of the Northern Corridor also mirrors a gradual thaw in relations between Moscow and Nato, which plunged to their lowest level since the end of the Cold War after Russia's brief war with Georgia in August.

However, Nato and the United States are simultaneously in talks on opening a third supply route through the secretive Central Asian state of Turkmenistan to prevent Russia from gaining a stranglehold on supplies to Afghanistan, the sources said. Non-lethal supplies, including fuel, would be shipped across the Black Sea to Georgia, driven to neighbouring Azerbaijan, shipped across the Caspian Sea to Turkmenistan and then driven to the Afghan border.

The week-long journey along this “central route” would be longer and more expensive than those through Pakistan or Russia and would leave supplies vulnerable to political volatility in the Caucasus and Turkmenistan.

The US and Nato are, though, exploring as many alternatives as possible as America prepares to deploy 20,000 more troops - three quarters of them by the summer - to add to the 67,000 foreign troops in Afghanistan. Turkmenistan represents the only realistic alternative that bypasses Russia. A route through Iran is out of the question because Washington does not have diplomatic relations with Tehran. Afghanistan's border with China is too remote to be used.

An agreement with Georgia has already been signed and negotiations with Azerbaijan are “ongoing”, a Nato official said.

Nato began exploring alternative supply routes in response to political instability in Pakistan last year and reached an informal agreement with Russia on the Northern Corridor at a Nato summit in Bucharest in April. At the same meeting President Berdymukhammedov of Turkmenistan offered to allow Nato to take supplies across its territory and to establish logistics bases there, according to Nato sources.

Negotiations stalled after the Georgian crisis, as Nato suspended high-level contacts with Moscow and Central Asian countries grew wary of angering the former Soviet master.

They have since shown their independence by refusing to back Moscow's recognition of South Ossetia and Abkhazia as independent states.

Russia, meanwhile, has been offering preferential treatment to Nato members that it considers “friendly”, such as France and Germany, the only Nato members allowed to fly supplies to Afghanistan through Russian airspace. In November Germany also became the first Nato member allowed to bring supplies for Afghanistan through Russia by railway.

Russian officials say that Moscow is ready to open the Northern Corridor to all Nato members as soon as the alliance finalises its agreements with Uzbekistan and Kazakhstan. The agreements cover non-military supplies such as fuel, food and clothing, and some non-lethal military equipment.

“All Nato countries will be able to use the Northern Corridor,” one Russian official familiar with the negotiations told The Times. “As far as we understand, Uzbekistan and Kazakhstan have agreed to it and sent the relevant papers to Brussels. We're just waiting for Nato to sign the agreements. We've done our part.”

BORDER WOES

A spate of attacks by Pakistani militants on supply convoys to Nato and US forces has caused backlogs and border closures (Jeremy Page writes). More than 1,000 trucks are stalled on the Afghan border and haulage costs are up by almost 70 per cent.Pakistani authorities have closed the border at Torkham, near the Khyber Pass, after militants set fire to at least 260 vehicles, including American Humvees, last weekend and attacked two cargo terminals in Peshawar on Thursday.

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